This section is from the book "The Boy Mechanic Vol. 2 1000 Things for Boys to Do", by Popular Mechanics Co.. Also available from Amazon: The Boy Mechanic, Vol2: 1000 Things for Boys to Do.
A simple adjustable bench stop for light work may be made from a piece of 1-in. broom handle and a piece of piano wire. Plane a flat surface on the broom stick and drill two 1/16-in. holes, about 1/4 in. deep, 1/4 in. from each end. Bend the ends of the wire to enter the holes and have the wire of such length as to give it a slight curve between the ends when it is in place on the stick.
Ill: The Spring Wire will Hold the Stop at Any Desired Position for Height
Bore a 1-in. hole through the bench top where it is desired to use the stop and cut several grooves, as shown, in the walls of the hole with a compass saw. The spring wire will slide into a groove and hold the stick wherever it is set. The position of the face can be changed by inserting the stick so that the wire will enter the right groove. - Contributed by Alan H. Andrews, Fall River, Mass.